Using physiological measures as independent indices of cognitive operations reflects the development of a relatively new field of inquiry. It has particular relevance to the study of memory disorders, as it permits evidence of mental operation despite no apparent retention. In addition, it allows for an independent assessment of the normalcy of processing characteristics during the performance of tasks on which amnesics do appear normal, e.g., implicit perceptual memory. To date, evidence for the existence of autonomic nervous system responses during a repetition priming study has been obtained with amnesic and physiological changes being noted during a face recognition task performed by a patient with prosopagnosia. These preliminary data suggest that this approach applied to other investigations of information processing deficits could have an extremely important outcome. Three main issues will be the focus of investigation in this proposal. First will be to determine whether or not amnesic patients orient appropriately to changes in stimuli that have inherent value (i.e., novelty) in enhancing later retrieval. Second, involves determining the extent to which specific instructions to orient to features that would enhance memory will change amnesics' response to those stimuli. Third, involves a systematic approach to assessing the amnesic's response to repeated stimuli during an implicit memory task. In order to study these three issues, five lines of research are proposed. The first explores the nature of the habituation of the orienting response. Study 2 explores the relative role of stimulus information vs. significance as factors in influencing amnesics' orienting response. The third experiment is designed to investigate amnesic patients' orientation to significant and/or novel stimuli within a continuous recognition task. Experiment 4 looks at repetition effects during a "data-driven" lexical decision task. Experiment 5 similarly explores these patients' orienting response during a "conceptually-driven" repetition lexical decision task. It is anticipated that the results of these investigations will permit an independent evaluation of amnesics' normalcy, or impairment, during the processing of information on tasks they can perform.